| Efficient use of renewable energy is one of the important means to deal with the energy and environment crisis.The combined cooling,heating and power system based on biomass not only use a kind of green energy,but apply cogeneration technology to improve energy efficiency of the system,which combines the advantages of the both,and has important research value.The system involves a few important subsystems,so this paper will discuss each subsystem separately and then study the characteristics of the whole system.Firstly,gasification experiments are carried out on fixed bed downdraft gasifier.Results show that comparing with wood chips,red wood pellets has higher carbon content and lower hydrogen content.The ignition time is longer but the temperature rises faster.Carbon monoxide,methane content in the syngas is higher than that of wood chips.In addition,the reaction temperature and the heating value of syngas is higher.The equivalent ratio has larger effect on the gasification reaction.It is found that when ER is equal to 0.22,the heating value reaches the maximum value of 1453kcal/m~3.The gas production rate increases from1.5m~3/kg-b to 2.03 m~3/kg-b,with an increase of 33%,and the gasification efficiency increases from 51.40%to 65.50%,slightly lower than the simulated results.But the overall gasification efficiency was relatively high,and the carbon conversion rate has been higher than 96%.Secondly,the simulation study was carried out,based on thermodynamic equilibrium model.Results show that with the increase of ER,the reaction temperature increases gradually,and the syngas's heating value first increases and then decreases.When the ER is equal to 0.24,the value reaches the maximum of 1605 kcal/m~3.When ER is equal to 0.30,the gasification efficiency reaches a maximum value of 76.76%.The moisture content(M)has little effect on the gasification reaction.But when M is too large,it makes the temperature too low,which deteriorates the gasification reaction more obviously.By the addition of sludge to change the biomass components,results show that the addition of sludge decreases hydrocarbon in biomass materials,and syngas heating value,gas production rate and gasification efficiency falls sharply.It can be seen that the effect of components on biomass gasification reaction is larger.Then,the internal combustion engine fueled by syngas is studied with AVL-Boost software.Results show that the maximum cylinder pressure is 3.281MPa,and the maximum combustion temperature is1780K,which are lower than the engine fueled by natural gas.Although the amount of fuel consumption is greater,the cost is lower.Its C~*is between 0.346 and 0.360 yuan/kW·h,while natural gas's C~*is between1.439 and 1.461 yuan/kW·h,so the engine fueled by syngas is more economic.The concentration of NO_x in exhaust gas of engine fueled by syngas is very low,but the concentration of CO and HC are higher than those of natural gas.The experimental results show that the maximum output power of the internal combustion engine is 12kW.The power generation efficiency of biomass gas internal combustion engine under different working conditions is lower than that of natural gas engine,and the maximum efficiency is 27%.At the same time due to more power dissipation,the residual heat of gas cylinder is also larger,and the exhaust gas temperature is lower.Finally,a new type of cogeneration system based on biomass is investigates.The primary energy ratio and exergy efficiency are lower than the traditional CCHP system,the largest energy efficiency and exergy efficiency were 52.1%?18.6%.The operating cost saving ratio can be lower than traditional CCHP under all conditions.The maximum operating cost saving ratio can reach 58.0%;the CCHP based on biomass can reduce carbon dioxide emissions,and increased with the increase of load,the maximum can reach 50.5%. |
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